Characterization of a partially purified preparation of estradiol-2 hydroxylase will be completed. An assay for estradiol-2 hydroxylase activity based on formation of tritiated water from 2-3H estradiol with partially purified enzyme preparation will be validated. The assay will then be used to evaluate the activity of estradiol-2 hydroxylase in various regions of the brain of rats and in a variety of reproductive states in the same species. The interaction between catechol-estrogens and tyrosine hydroxylase will be studied in an adrenergic neuroblastoma tissue culture.